Method and device for inspecting transparent containers

ABSTRACT

A process for inspecting transparent containers (B), in which every container is illuminated and at least two exposures of the same container are produced by means of a single CCD camera (K) and evaluated, whereby one exposure images the container profile and the other exposure images the container wall, the exposure time of the CCD camera (K) is changed, between the two exposures, from an exposure time for a container to an exposure time for a container profile. A control device (C 2 ) for changing the sensitivity of exposure of the CCD camera (K) is produced.

REFERENCE TO RELATED APPLICATIONS

This disclosure claims the benefit of the filing date of InternationalApplication No. PCT/EP01/03237, having an international filing date ofMar. 21, 2001, which designated the United States of America, and thisdisclosure is the United States national stage of that internationalapplication. This disclosure further claims priority to Germany patentapplication 100 27 226.6, filed May 31, 2000.

FIELD OF THE INVENTION

The invention relates to a process and a device for inspectingtransparent containers in beverage bottling operations.

BACKGROUND OF THE INVENTION

In the inspection of transparent containers, particularly beveragebottles, two camera systems and at least two illumination systems, ifapplicable, are, as a general rule, used in order to carry out theevaluation of the container wall (inspecting of the side wall) and theevaluation of the container contour, because an illumination other thanthe one used for the evaluation of the wall is necessary for theevaluation of the contour. The inspection device is thus made moreexpensive by the two camera systems. In addition, the expense formaintenance is high (DE 19 904 732 A).

In the German patent document DE 19 904 732 A, it is proposed to use asingle CCD camera for the two exposures, to use a maximum intensity ofillumination for the exposure of the wall of the container, and toreduce the intensity of illumination for the exposure of the contour ofthe same container.

SUMMARY OF THE INVENTION

The task which forms the basis of the invention is that of devising aprocess of the type stated above, as well as a device that is suitablefor carrying out the process, by means of which a reliable evaluation ofthe wall and evaluation of the contour are possible in another way bymeans of one single CCD camera.

Both the optimally exposed image of the wall, as well as the optimallyexposed image of the contour, can be produced by changing thesensitivity of exposure of the single CCD camera. The sensitivity ofexposure is, as a variable process parameter, important precisely inregard to the presuppositions which are decisive for the quality of bothof the exposures precisely at the point where the images ultimatelyarise—that is to say, in the CCD camera. In this way, optimally exposedimages of the contour and of the wall are formed, from which a highreliability of evaluation results. It is obvious that the container thatis inspected during the inspection can, if necessary, be rotated inorder to obtain, with several first and second exposures, acomprehensively complete image of the wall of the container or of thecourse of contour of the container. A container can, however, also bedepicted over its full circumference by means of only a single first andsecond exposure if optical devices, such as mirror apparatuses or thelike, are used, which devices simultaneously produce several images ofthe container, exposed in a circumferentially-shifted manner, in only asingle camera image. Suitable apparatuses, such as in WO 95/0427, forexample, are already known.

The device manages to work with a single CCD camera, the sensitivity ofexposure of which is modified in such a manner that the image of thewall and the image of the contour are exposed in an optimal manner. Eventhe smallest damages to or contaminations of the wall, or deviations inthe contour, can also be determined with only a minimal expense forequipment. In addition, the device is maintenance-friendly, because fewcomponents that require maintenance are present.

The specific first and second exposure are formed, in a manner that issimple in terms of technical process, at the same intensity ofillumination. The illumination can take place, in a preferred manner, bymeans of flashes, such as by means of an LED luminous screen, forexample. An expensive, controllable illumination device, with zones ofbrightness which can be adjusted in different manners, is not necessary.

The exposures of a container taking place in a time-staggered manner arestored in memory, whereby the evaluation (contour, wall) can be carriedout later, in either a temporally parallel or a sequential manner.

In accordance with the device, a control device is used , which devicechanges the sensitivity of exposure of the CCD camera by changing theexposure time in an optimized or in an alternating manner, as the casemight be. This can be brought about, in several trigger positions, bymeans of an electronic control circuit.

The source of illumination is, in a suitable manner, at least one LEDradiant field which can, in a preferable manner, be activated inindividual flashes. In this manner, the images can be produced withgreat sharpness and at a uniform exposure.

The source of illumination of the CCD camera can either be positioned onopposite sides of the path of movement of the container (examination oftransmitted light), or else on the same side (examination of incidentlight).

BRIEF DESCRIPTION OF THE DRAWINGS

One form of implementation of the object of the invention is illustratedby means of the diagrams. These depict the following:

FIG. 1: In schematic terms, a cross-section through a device forinspecting transparent containers;

FIG. 2: A schematic view from above of FIG. 1;

FIG. 3: In schematic form, an exposure of the wall; and:

FIG. 4: In schematic form, an exposure of the contour of the container.

DETAILED DESCRIPTION OF THE INVENTION

In a device (V) for inspecting transparent containes (B), such asbeverage bottles of glass or of plastic, for example, each container (B)in a series of containers being continuously moved forward is inspected,during its passage through the device, in regard to the quality of itscontainer wall (W), as well as the contour (P) of the same. Containerswith contaiminations and/or damages and/or impermissible deviations intheir contour should be detected and subsequently separated out. Eachcontainer (B) is transported through an inspection area on a conveyingdevice (F). The conveying device (F) has two conveyor belts (1, 2), forexample, which are driven in the same direction but at different speeds,in order to simultaneously rotate the container (B) around its verticalaxis during the transport movement. A source of illumination (L), suchas at least one LED radiant field (3), for example, which source can beactivated to individual flashes by means of an electronic control device(C1), is positioned on one side of the conveying device (F). Forexample, a single CCD camera (K) is positioned on the opposite side andoriented towards the inspection area in which the exposure of thecontainer are formed and, in specific terms, two different exposures aremade, namely, an exposure of the wall and an exposure of the contour,each in an alternating manner. An electronic control device (C2) isprovided for the CCD camera.

An evaluation device (A) connected with the single CCD camera (K), inwhich device the images of the wall and the images of the contour areevaluated, can additionally be seen in the schematic view from above ofFIG. 2. Upon the determination of a contamination and/or damage and/or adeviation in contour, a separating device (S) is activated, which deviceconveys the container (B) in question into a given area (4) (collectingbin, or the like).

A sensor (5), which can, for the clocking of the source of illumination(L) of the CCD camera (K), be connected with the control devices (C1,C2), is provided at the start of the inspection area. The controldevices can additionally be connected with a rotational pacesetter ofthe drive unit (6) of the conveying device (F) in order to follow thecontainer (B) in the inspection area in a manner dependent upon theconveying speed. This is suitable, for example, if several exposures ofone container are to be carried out in different rotational positions.Trigger positions of a hardware type or of a software type (T1, T2) aretaken into consideration during the inspection in order, for example, tochange the sensitivity of exposure of the CCD camera (K), by means ofthe control device (C2), between the first and thesequentially-following second exposures in an alternating manner, insuch a way that, in one exposure of the wall (first exposure), adifferent sensitivity of exposure is set than in another exposure of thecontour (second exposure). In this, it is suitable to consider severaltrigger positions, such as in a multiple exposure of a container, forexample.

In FIG. 3, an exposure of the wall of the container (B) is depictedschematically, in which, by adjusting the sensitivity of exposure—thatis to say, the exposure time—of the CCD camera (K), an optimal exposureis provided for detecting contaminations and/or damages (X) either on orin the wall (W) of the transilluminated container, as the case may be.In actual practice, the image of the exposure of the wall is not optimalfor the determination of the contour of the container. Normally, anillumination that is suitable for the exposure of the wall provides animage from which the outline of the container can only be detected withdifficulty, which image is too bright for inspecting the contour.

In the exposure of the contour in FIG. 4, on the other hand, the contour(P) of the container (B) is imaged in a sharp and meaningful manner, asrepresented by the solid outline, in order to detect deviations (Y) inthe contour. In the exposure of the contour, the wall itself is notimaged in a manner which is sufficiently detailed in detection of flakesof dirt, etc. An exposure which is sufficient for inspecting the contouris, as a general rule, too dark for inspecting the wall.

If necessary, not only is the sensitivity of exposure of the CCD cameramodified in such a manner that the exposures of the wall are exposed inan optimal manner for the exposure of the contour, but the intensity ofillumination is also strongly modified for the equalization of differentlevels of transparency of the container through the fact, among otherpoints, that the flash of the LED radiant field (3) is modified by meansof the control device (C1), for example.

The sensitivity of the exposure or the exposure time for the container(B) which is optimal for the specific exposure of the wall or theexposure of the contour, respectively, is set in advance. During theinspection, the sensitivity of exposure is then adjusted back and forthbetween the values set in an alternating manner. By this means, it isthereby possible to scan the specific level of transparency of thecontainer which is to be inspected, and to then set the specificallyoptimal trigger position (T1 or T2) or the sensitivity of exposurecorresponding to this trigger position, as the case may be. In a similarmanner, the flash time for the exposure of the wall or for the exposureof the contour, as the case may be, can be adjusted in an individualmanner.

1. A process for inspecting transparent containers (B), comprising thesteps of illuminating every container (B) and producing by a single CCDcamera at least two exposures of the same container, evaluating theexposures by an evaluation device, imaging a contour of the containerwith one exposure for the evaluation of the contour, imaging a wall ofthe container with another exposure for the evaluation of the wall, andchanging over, between the two exposures, the exposure time of the CCDcamera (K) from an exposure time for the container wall to an exposuretime for the container contour.
 2. A process in accordance with claim 1,further comprising the step of forming the two exposures in the sameintensity of illumination.
 3. A process in accordance with claim 2,wherein the step of forming the two exposures in the same illuminationintensity is performed by means of flashes.
 4. A process in accordancewith claim 1, further comprising carrying out and storing in memory thetwo exposures of a container (B) one immediately after the other, andcarrying out the evaluation of the exposures in one of in parallel or insuccession, one after the other.
 5. A device (V) for inspectingtransparent containers (B), comprising in combination acontainer-conveying device (F), at least one source of illumination (L),a single CCD camera (K ) which is connected with an evaluation device(A) for one or more exposures of the containers, one or more exposuresof the container walls and one or more exposures of the containerprofiles being produced by means of said CCD camera (K), and a controldevice (C2) for changing the sensitivity of exposure of said CCD camera(K) between a sensitivity of exposure for the container profile and asensitivity of exposure for the container walls.
 6. A device inaccordance with claim 5, wherein said control device (C2) has at leastone electronic control circuit, by means of which the exposure time ofsaid CCD camera (K) can be changed in at least two trigger positions(T1, T2).
 7. A device in accordance with claim 5, wherein said source ofillumination (L) comprises at least one LED radiant field (3) which canbe activated in individual flashes.
 8. A device in accordance with claim7, further comprising a flash time adjusting device (C1) which iscoordinated with said LED radiant field (3).
 9. A device in accordancewith claim 8, wherein said flash time adjusting device (C1) is anelectronic control circuit which adjusts a flash time for a change ofthe intensity of illumination by means of different trigger positions.